Wire and cable can be said to be everywhere, and its importance cannot be overemphasized. Some people say it is the blood vessel of industry, the nerve of society, and some people say it is the heart of the motor. In the project, wire and cable is a very important main material. Regardless of which link in the bidding, budget, and final accounts, the change in the price of wire and cable will greatly affect the cost of the entire project. Then understand the basic knowledge of wire and cable and price adjustment, it is essential.

First, the classification and basic structure of wire and cable

1. Classification of wire and cable

There are thousands of types of wire and cable products, which are used in all walks of life. They are generally used in two ways, one is to transmit current, and the other is to transmit signals.

The main technical performance indicators of the transmission current cable are conductor resistance and voltage resistance. The main control technical performance indicators of transmission signal cables are transmission performance - characteristic impedance, attenuation and crosstalk. Of course, the transmission signal mainly relies on current (electromagnetic wave) as the carrier, and now with the development of science and technology, light waves can be used as the carrier for transmission.

In general, the cable can be divided into six categories: (1) bare wire class (2) electromagnetic wire (enamelled wire)(3) power cable (4) electrical equipment wire and cable (5) communication wire and cable (6) optical cable.

2, cable basic structure

The most basic structure of the general cable has a conductor, insulation layer and outer protective layer, according to the requirements to add this structure, such as shielding layer, inner protective layer or armored layer, in order to have the roundness of the cable and then add some filling materials. Conductors are carriers that transmit current or signals, and other structures are used for protection. The performance of protection according to the needs of cable products in general, there are three kinds, one is to protect the cable itself units do not interact with each other or reduce the impact, such as voltage resistance, heat resistance, anti-electromagnetic field loss, communication cable anti-signal interference and so on. The other protection is to protect the current in the conductor does not affect the outside, such as preventing the leakage of current, electromagnetic wave leakage and so on; The utility model provides protection against external influences on the interior of the cable, such as pressure resistance, tension resistance, heat resistance, weather resistance, fire resistance, water resistance, electromagnetic wave interference resistance, etc.

The following is a brief introduction to the structural units of power cables.

1) Conductor (or conductor core)

Its function is to conduct an electric current. There are solid core and stranded points. Materials are copper, aluminum, silver, copper clad steel, aluminum clad steel, etc., the main use is copper and aluminum. Copper conducts electricity much better than aluminum. The national standard requires that the resistivity of copper conductor is not less than 0.017241ωmm2 /m(20℃), and the resistivity of aluminum conductor is not less than 0.028264ωmm2 /m(20℃).

2) Refractory layer

Only fire-resistant cables have this structure. Its role is that the cable can withstand a certain time in the fire, giving people more time to use electricity when they escape. The material used today is mainly mica tape. In a fire, the cable will burn quickly, because the mica sheet of the mica tape is resistant to high temperature and has an insulating effect, which can protect the conductor from running for a certain time in a fire.

3) Insulation layer

Coated in the conductor, its role is to isolate the conductor, withstand the corresponding voltage, to prevent current leakage.

There are many kinds of insulating materials, such as polyvinyl chloride (PVC), polyethylene (PE), cross-linked polyethylene (XLPE), rubber (there are many kinds of rubber, butadiene rubber, neoprene rubber, styrene butadiene rubber, ethylene propylene rubber, etc.), fluorine plastics, nylon, insulating paper and so on. The main performance of these materials is good insulation performance, other performance requirements according to the cable requirements are different, some require the dielectric coefficient to be small, to reduce loss, some require flame retardant performance or high temperature resistance, some require the cable will not or less produce smoke or harmful gases when burning, some require oil resistance, corrosion resistance, and some require softness.

4) Shielding layer

Outside the insulation layer and inside the outer protective layer, the role is to limit electric field and electromagnetic interference.

For different types of cables, shielding materials are not the same, mainly: copper wire braid, copper wire winding, aluminum wire (aluminum alloy wire) braid, copper tape, aluminum foil, aluminum (steel) plastic tape, steel tape and other wrapping or longitudinal wrapping.

5) Fill layer

The role of filling is mainly to make the cable rounded and stable in structure, and the filling of some cables also plays the role of water resistance and fire resistance. The main materials are polypropylene rope, glass fiber rope, asbestos rope, rubber, etc., there are many kinds, but there is a main performance requirement of non-hygroscopic materials, of course, can not conduct electricity.

6) Inner cover

The function of the inner sheath is to protect the insulated wire core from being damaged by the armor layer or the shield layer.

The inner cover has several forms, such as extruded wrap, wound wrap and longitudinal wrap. For the high requirements, the form of extrusion wrap is used, and the form of winding or longitudinal wrap is used for the low requirements. Now the materials used for wrapping are also diverse, such as the inner sheath of steel tape armor, which is wrapped with PVC tape, and polypropylene tape (very thin, the surface is made of particles raised to the thickness). Can it be used? It is mainly the market positioning problem of cable product quality. This is the same as whether silane cross-linked insulated wire core is differentiated by color or by color band, and the nature is some of the same, but not all of the same. Here, the use of PVC tape and polypropylene tape has an impact on product quality. Silane cross-linked insulated wire core using color to distinguish or using color band to distinguish, has little impact on product quality, mainly depends on the needs of users.

7) Armor layer

Armor layer is used to protect the cable from external damage. The most common are steel tape armor and steel wire armor, as well as aluminum tape armor, stainless steel tape armor and so on. The main function of steel band armouring is compression, and steel wire armouring is mainly tensile. According to the size of the cable, the thickness of the steel tape for armor is not the same, which is specified in each cable standard.

8) Outer protective layer

The part that protects the outermost layer of a cable. There are three main types: plastic, rubber and metal. Among them, the most commonly used plastics are polyvinyl chloride plastics, polyethylene plastics, and according to the characteristics of the cable, there are flame retardant types, low smoke and low halogen types, low smoke halogen free types.

Second, the use of various cables and specifications, representations

The representation of wire and cable is mainly composed of three parts: model, specification and standard number.

1. The meaning of the model

The models of electrical equipment wire and cable and power cable are mainly composed of the following seven parts, and some special wire and cable models have derived codes.

Here is the meaning of the letters in the most commonly used wire and cable models.

Letter 1: Category, purpose

Letter Category, Use Letter category, use

B Wiring JK overhead

SY Coaxial cable R Flexible cable

A Install YFD prefabricated branch cables

ZR Flame retardant H local communication cable

DDZ low smoke low halogen flame retardant NH refractory

DJ Computer cable WDZ Low smoke halogen-free flame retardant

K control P signal cable

Unmarked power cable

Letter 2: for conductor (core)

L stands for "aluminum," not copper

Letter 3: indicates insulation material

V stands for "polyvinyl chloride" Y stands for "polyethylene" YJ stands for "crosslinked polyethylene"

X stands for "rubber," Z stands for "oil-impregnated paper," and F stands for "fluoroplastic."

Letter 4: for inner sheath

V stands for "Polyvinyl chloride sheath" Y stands for "polyolefin" Q stands for "lead sheath"

L stands for "Aluminum package" H stands for "rubber sleeve"

Letter 5: Structural features

R for "Soft" and S for "twisted"

Number 6: Outer sheath or derivative

Digital marking armour layer outer coat or outer sheath

0 None --

1 Interlocking armored fiber outer quilt

2 Double layer steel with PVC jacket

3 Fine round steel wire polyethylene jacket

4 thick round steel wire --

5 Corrugated (rolled) steel strip --

6 double aluminum (or aluminum alloy) tape --

7 Copper wire braid --

8 Wire braid --

2, the most commonly used electrical equipment with wire and cable and power cable model examples

VV - Copper core polyvinyl chloride insulated polyvinyl chloride sheathed power cable

VLV - Aluminum core PVC insulated PVC sheathed power cable

YJV22 - Copper core XLPE insulated steel tape armoured PVC sheathed power cable

KVV - PVC insulated PVC sheathed control cable

227IEC 01(BV) - BV for short, single-core hard conductor unsheathed cable for general purpose

227IEC 02(RV) - RV for short, general purpose single-core flexible conductor unsheathed cable

227IEC 10(BVV) - BVV for short, lightweight PVC sheathed cable

227IEC 52(RVV) - Short for RVV, lightweight PVC sheathed flexible cord

227IEC 53(RVV) - RVV for short, common PVC sheathed flexible cord

BV - copper core PVC insulated wire

BVR - copper core PVC insulated flexible cable

BVVB - Copper core PVC insulated PVC sheathed flat cable

JKLYJ - Crosslinked polyethylene insulated overhead cable

YC, YCW - heavy rubber sheathed flexible cable

YZ, YZW - medium rubber sheathed flexible cable

YQ, YQW - lightweight rubber sheathed flexible cable

YH - Welding machine cable

3. Specifications

The specification is composed of rated voltage, number of cores and nominal cross section.

The rated voltage of medium and low voltage power cables is generally 0.6/1kv, 1.8/3kv, 3.6/6kv, 6/6(10)KV, 8.7/10(15)kv, 12/20kv, 18/20(30)kv, 21/35kv, 26/35kv and so on.

The number of cores of wire and cable is determined according to actual needs, the general power cable mainly has 1, 2, 3, 4, 5 cores, the wire is mainly 1 to 5 cores, and the control cable has 1 to 61 cores.

The nominal cross section is an approximation of the cross section of the guide body. In order to achieve the specified DC resistance, it is convenient to remember and unify an integer value near the cross section of a conductor. China's unified provisions of the conductor cross-section 0.5, 0.75, 1, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240, 300, 400, 500, 630, 800, 1000, 1200 and so on. It should be emphasized here that the nominal cross section of the conductor is not the actual cross section of the conductor, many of the actual cross sections of the conductor are smaller than the nominal section, and several are larger than the nominal section. In the actual production process, as long as the DC resistance of the conductor can meet the specified requirements, it can be said that the cross section of the cable is up to standard.

Third, the main materials of cable

1. Copper wire

The copper wire made by continuous casting and rolling process using electrolytic copper as raw material is called low-oxygen copper wire. Copper wire produced by up-drawing method is called anaerobic copper wire.

The oxygen content of low-oxygen copper wire is 100~250ppm, the copper content is 99.9~9.95%, and the conductivity is 100~101%.

The oxygen content of the oxygen-free copper wire is 4~20ppm, the copper content is 99.96~9.99%, and the conductivity is 102%.

The specific gravity of copper is 8.9g/cm3.

2. Aluminum wire

The aluminum wire used for wire should be annealed and softened, and the aluminum wire used for cable is generally not softened.

The resistivity of aluminum for wire and cable is required to reach 0.028264ωmm2 /m, and the specific gravity of aluminum is 2.703g/cm3.

3, polyvinyl chloride (PVC)

Polyvinyl chloride plastic is based on polyvinyl chloride resin and mixed with various adjuvants, such as antioxidants, fillers, brighteners, flame retardants, etc., and its density is about 1.38 ~ 1.46g/cm3.

PVC material features: excellent mechanical properties, chemical corrosion resistance, no delay, good weather resistance, good electrical insulation performance, easy processing and so on. The disadvantages of PVC material: ① a lot of toxic smoke emitted when burning; ② Poor thermal aging performance. PVC is divided into insulating material and sheathing material.

4, polyethylene (PE)

Polyethylene is made of refined ethylene polymerization, according to density can be divided into low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE).

The density of low density polyethylene is generally 0.91~0.925g/cm3; The density of medium density polyethylene is generally 0.925~0.94g/cm3; The density of high-density polyethylene is generally 0.94~0.97g/cm3.

Advantages of polyethylene material:

① High insulation resistance and voltage resistance;

(2) The dielectric constant ε and the dielectric loss Angle tangent tgδ are small in the wide frequency band;

(3) Rich flexibility, good wear resistance;

④ Good heat aging performance, low temperature performance and chemical stability;

⑤ Good water resistance, low moisture absorption rate;

⑥ The cable made with it is light in weight and easy to use and lay.

Disadvantages of polyethylene material:

① Easy to burn when in contact with flame;

② The softening temperature is low.

5, Cross-linked polyethylene (XLPE)

There are two main types of crosslinked polyethylene used in the wire and cable industry. One is a silane crosslinking agent, called silane crosslinking material, which is mainly used in the insulation layer of low-voltage wire and cable. The other is a crosslinked polyethylene material with diisopropylbenzene peroxide (DCP) as a crosslinking agent, which is mainly composed of polyethylene, crosslinking agent and antioxidant. Mainly used in the insulation layer of medium and high voltage cables, the higher the insulation pressure level, the higher the purity is required.

DCP is a kind of peroxide, the higher the temperature, the faster the decomposition, and the decomposition will catalyze the crosslinking reaction of polyethylene. DCP will also decompose at room temperature, but the decomposition rate is very slow, but it will decompose rapidly when heated to a certain temperature (temperature above 125 ° C).

Qingdao Tianxing Cable Co., Ltd. focuses on the production of customized wire and cable manufacturers, main: fire wire and cable, power cable, control cable and other products, exported to more than 40 countries and regions around the world, the annual production capacity of 1 billion yuan. 6000 square meters of storage, standing hundreds of millions of inventory, order demand for rapid distribution and delivery, large prices more favorable. Hotline: 16678668098